German Pat. No. 277,648 of Apr. 28, 1908 discloses a process using a dyeing bath based on organic solvents such as hydrocarbons, carbon tetrachloride, and the like.
Italian Pat. No. 872,658 discloses a dyeing process for fibrous materials containing --NH-- groups, characterized in that the dyeing is carried out with solutions based on chlorinated hydrocarbons containing aminic salts or aminic adducts of the acid dyes with amines containing at least eight carbon atoms and showing an uninterrupted chain of at least three carbon atoms.
However, it has been found experimentally that with the amines disclosed in the above said Italian patent it is not possible to obtain dyeings with an intensity greater than 2-3% of dye on the weight of the fibre, with commercially acceptable exhaustion rates of the dyeing baths.
This is also confirmed by what was ascertained and maintained by V. Yoshio Nemoto et al. in: "Dyeing Of Wool And Nylon With Complexes Of Acid Dyes With Amines From Organic Solvents," that is, that the above-described known method "contains many problems difficult to overcome before it can be used successfully" (see text: Solvent Technology -- Update `73 AATCC -- American Association of Textile Chemistry and Colorists -- Symposium 1973, pages 58-64).
Moreover, it is known that the longer the hydrocarbon chain of the amine, and thus the higher the solubility in an organic solvent of the complex with acid dye, the smaller will be the degree of exhaustion (see Yoshio Nemoto, loc. cit.)
In the prior art there is not disclosed the use of salts or complexes of acid dyes with aliphatic amines, in which the primary or secondary nitrogen atom be combined with a tertiary alkyl radical.